Connections in urban medium and low-voltage underground power distribution systems, such as between cables and transformers, are generally accomplished with some form of multiple cable junction. Such multiple cable junctions typically distribute medium or low voltage from a main feeder cable to multiple cable taps, which in turn routes power to multiple users. Conventional cable junctions for this purpose, known in the field as “junction crabs,” generally consist of a unitary mass of epoxy enclosing an electrically conductive network therein and having multiple tap branches extending therefrom and fusible elements for each branch integrally molded therein. Thus, each branch includes a permanently connected fuse link, which is typically hard-wire connected to a respective tap cable.
A typical urban utility experiences approximately 1,500 failures on its network feeders each year. Such network failures are often caused by power surges in the system, which may result in one or more of the fuse elements within the “crab” being blown. Since there is no indication provided with such conventional junctions, the first problem in correcting the network failure is to find the blown fuse. The circuit configuration for most utility networks is designed to maintain service to the maximum number of customers during faults by having multiple sources and fused junctions. This makes the location of a blown fuse difficult. In addition, contamination from the blown fuse link often provides false readings when typical voltage or continuity measurements are attempted.
The second problem is replacement. As described above, conventional construction of multiple cable junctions is based on permanently connected fuse links. Therefore, if any one of the fuse links blows, the feeder cable feeding the junction must first be deenergized and the entire defective junction must be cut out of the circuit and a new unit spliced in. This means that the multiple users fed by the feeder cable remain out of service while the junction is replaced. Each feeder outage duration is directly proportional to the risk of power customer interruption and the stress experienced by other feeders and transformers in the network. Obviously, this conventional procedure results in undesirable long system outage time.
Accordingly, it would be desirable to provide a multiple cable junction for distributing low voltage power from a main feeder to multiple cable taps, wherein the junction provides indication for individual blown fuses and wherein a blown fuse can be easily replaced without substantially disrupting service to the other tap branches.